Luminance (Unit: lumen) is the intensity of light emitted from a surface per unit area in a given direction that is the physical measure of the subjective sensation of brightness.

Reference Definition by Wikipedia: Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted or reflected from a particular area, and falls within a given solid angle. The SI unit for luminance is candela per square metre (cd/m2). A non-SI term for the same unit is the “nit”. The CGS unit of luminance is the stilb, which is equal to one candela per square centimetre or 10 kcd/m2.

Related Definitions in the Project: The Property and Unit